This disclosure generally relates to inspection equipment and methods, and deals more particularly with methods and apparatus for inspecting structures having irregular and variable shapes, especially soft-tooled structures made of composite material.
A variety of elongated composite structures may have relatively confined internal cavities that require inspection in order to assure that the structure meets production and/or performance specifications. The composite radii formed using tooling are not always well defined and may vary from part to part. In some cases, dimensional or contour variations may make reliable inspection using conventional methods more challenging. In view of the deviation from circularity of tooled composite radii, the term “radius” as used hereinafter should be construed non-strictly to include circular profiles and curved profiles which deviate from circularity.
The desire to maximize performance and minimize weight in commercial aircraft has resulted in designs with varying radii that may be implemented in either hard or soft tooling. Soft tooling produces inspection surfaces that vary in an unpredictable manner, within limits, but beyond the tolerance limits of fixed-probe ultrasonic inspection methods. Designed radius changes also vary beyond the limits of fixed-probe methods. New low-turbulence aerodynamic shapes present continuously changing complex surfaces for inspection. Existing fixed probes are not capable of inspecting some surfaces.
The foregoing design methodology creates part structures whose radius dimensions vary along the length of the part. There are also a vast amount of individual composite parts with unique radius dimensions. Whether inspecting multiple parts with many radii or a single part with multiple radii, operators consume large amounts of time to adjust their probes to the different radius dimensions. In addition, the designers of the non-destructive inspection (NDI) systems have to design and fabricate unique probes for the variety of radius shapes.
In particular cases the problem can be solved by using several fixed probes, by using a probe that is manually adjustable or by using a probe that automatically mechanically adjusts during probe scanning. Operators have to adjust the probe while inspecting multiple radii or varying radii. The distance between the radius array probe and the composite radii structure dictates the signal integrity while performing an ultrasonic inspection. One method is to align the ultrasonic probe on a concentric circle with respect to the part radii. Should the radius of the part change, the position of the probe would also need to change.
An NDI system capable of inspecting multiple or varying radii without mechanically adjusting for changes in the radius dimension would be useful.